During January’s Critical Mass there was considerable interest in the little red boom-box strapped to my bike…

What’s inside? How did you make it? Is it complicated? Can I make one?

In an attempt to answer these questions, I’m going to begin by being completely honest and telling you that I didn’t make it. The inventor/mastermind is a guy called Jethro who was kind enough to lend it to us. Jethro built the wee boom-box for Critical Mass down in his native Brighton, but since moving to Edinburgh he now has to work on Friday nights and so can’t come along to our rides.

The genius of Jethro

Under the bonnet you can see what we’re working with. The (grey) rectangle to the right is a 12Volt/7Ah lead-acid battery, which is connected to the (red) Sony Xplod 444Watt amplifier, and then on to the speakers (the black circles at…